Tag: recent single origin hypothesis

October 4, 2014 / Greg Giles / Comments Off on Does the discovery of 1.77-million-year-old skeletons rewrite history? ~ Video

Dr Lordkipanidze and colleagues The latest discoveries the 1.77-million-year-old skeletons of three adults and a teenager have legs and feet adapted for long-distance walking and running, similar to those of modern humans, but have hands and arms ...

In 1987, a group of genet­icists published a surprising study in the journal Nature.­ The­ researchers examined the mitochondrial DNA (mtDNA) taken from 147 people across all of today's major racial groups. These researchers found that the lineage of all people alive today falls on one of two branches in humanity's family tree. One of these branches consists of nothing but African lineage, the other contains all other groups, including some African lineage.­Even more impressive, the geneticists concluded that every person on Earth right now can trace his or her lineage back to a single common female ancestor who lived around 200,000 years ago. Because one entire branch of human lineage is of African origin and the other contains African lineage as well, the study's authors concluded Africa is the place where this woman lived. The scientists named this common female ancestor Mitochondrial Eve.­The researchers got the idea for this project based on a discovery another geneticist made in 1980. Dr. Wesley Brown noticed that when you compare the mtDNA of two humans, th­e samples are much more similar than when the mtDNA of two other primates -- for example, two chimpanzees -- is compared. Brown found, in fact, that the mtDNA of two humans has only about half as many differences as the mtDNA of two other primates within the same species [source: Cann]. This suggests that humans share a much more recent common ancestor than other primates do, an idea tantalizing enough to launch the Nature investigation.The study's lead author, Rebecca Cann, called her colleagues' and her choice to use Eve as the name "a playful misnomer," and pointed out that the study wasn't implying that the Mitochondrial Eve wasn't the first -- or only -- woman on Earth during the time she lived [source: Cann]. Instead, this woman is simply the most recent person to whom all people can trace their genealogy. In other words, there were many women who came before her and many women who came after, but her life is the point from which all modern branches on humanity's family tree grew.When the researchers in the 1987 study looked at samples taken from 147 different people and fetuses, they found 133 distinct sequences of mtDNA. A few of the people sampled, it turned out, were recently related. After comparing the number of differences among the mtDNA samples within races, they found that Africans have the most diversity (that is, the most number of differences) of any single racial group. This would suggest that the mtDNA found in Africans is the oldest: Since it has had the most mutations, a process which takes time, it must be the oldest of lineages around today.The two distinct branches they discovered contained the mtDNA found in the five main populations on the planet: African, Asian, European, Australian and New Guinean. Researchers found that in the branch that was not exclusively African, racial populations often had more than one lineage. For example, one New Guinean lineage finds its closest relative in a lineage present in Asia, not New Guinea. All of the lineages and both of the two branches, however, can all be traced back to one theorized point: Mitochondrial Eve.So how did Eve end up being humanity's most recent common ancestor? We'll look at that in this article, as well as some arguments lodged against the Mitochondrial Eve theory. But first, what are mitochondria and why do scientists use mtDNA to track lineage?View Article Here Read More

This abstract cave carving is possibly the first known example of Neanderthal rock art. The etching covers an area of about 47 square inches (300 square centimeters). Stewart Finlayson

news.discovery.comAround 39,000 years ago, a Neanderthal huddled in the back of a seaside cave at Gibraltar, safe from the hyenas, lions and leopards that might have prowled outside. Under the flickering light of a campfire, he or she used a stone tool to carefully etch what looks like a grid or a hashtag onto a natural platform of bedrock.

Archaeologists discovered this enigmatic carving during an excavation of Gorham's Cave two years ago. They had found Neanderthal cut marks on bones and tools before, but they had never seen anything like this. The researchers used Neanderthal tools to test how this geometric design was made — and to rule out the possibility the "artwork" wasn't just the byproduct of butchery. They found that recreating the grid was painstaking work.

"This was intentional — this was not somebody doodling or scratching on the surface," said study researcher Clive Finlayson, director of the Gibraltar Museum. But the discovery poses much more elusive questions: Did this engraving hold any symbolic meaning? Can it be considered art?

Close cousins

Neanderthals roamed Eurasia from around 200,000 to 30,000 years ago, when they mysteriously went extinct. They were the closest known relatives of modern humans, and recent research has suggested that Neanderthals might have behaved more like Homo sapiens than previously thought: They buried their dead, they used pigments and feathers to decorate their bodies, and they may have even organized their caves.

Despite a growing body of evidence suggesting Neanderthals may have been cognitively similar to modern humans, a lack of art seemed to be the "the last bastion" for the argument that Neanderthals were much different from us, Finlayson said.

Archaeologists recently pushed back the date of hand stencil paintings found at El Castillo cave in northern Spain to 40,800 years ago, which opens the possibility that Neanderthals created this artwork. But there is no solid archaeological evidence to link Neanderthals to the paintings.

Gorham's Cave

In Gorham's Cave, Finlayson and colleagues were surprised to find a series of deeply incised parallel and crisscrossing lines when they wiped away the dirt covering a bedrock surface. The rock had been sealed under a layer of soil that was littered with Mousterian stone tools (a style long linked to Neanderthals). Radiocarbon dating indicated that this soil layer was between 38,500 and 30,500 years old, suggesting the rock art buried underneath was created sometime before then.

Gibraltar is one of the most famous sites of Neanderthal occupation. At Gorham's Cave and its surrounding caverns, archaeologists have found evidence that Neanderthals butchered seals, roasted pigeons and plucked feathers off birds of prey. In other parts of Europe, Neanderthals lived alongside humans — and may have even interbred with them. But 40,000 years ago, the southern Iberian Peninsula was a Neanderthal stronghold. Modern humans had not spread into the area yet, Finlayson said.

To test whether they were actually looking at an intentional design, the researchers decided to try to recreate the grid on smooth rock surfaces in the cave using actual stone tools left behind in a spoil heap by archaeologists who had excavated the site in the 1950s. More than 50 stone-tool incisions were needed to mimic the deepest line of the grid, and between 188 and 317 total strokes were probably needed to create the entire pattern, the researchers found. Their findings were described yesterday (Sept. 1) in the journal Proceedings of the National Academy of Sciences.

Finlayson and his colleagues also tried to cut pork skin with the stone tools, to test whether the lines were merely the incidental marks left behind after the Neanderthals had butchered meat. But they couldn't replicate the engraving.

"You cannot control the groove if you're cutting through meat, no matter how hard you try," Finlayson said. "The lines go all over the place."

A simple grid is no Venus figurine

The Neanderthals' brand of abstract expressionism might not have impressed Homo sapiens art critics of the day.

"It's very basic. It's very simple," said Jean-Jacques Hublin, director of the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology in Germany. "It's not a Venus. It's not a bison. It's not a horse."

By the late Stone Age, modern humans who settled in Europe were already dabbling in representational art. At least a dozen different species of animals — including horses, mammoths and cave lions — are depicted in the Chauvet Cave paintings, which are up to 32,000 years old. The anatomically explicit Venus figurine discovered at Hohle Fels Cave in southwestern Germany dates back to 35,000 years ago. Other busty female statuettes — the Venus of Galgenberg and the Venus of Dolní Vestonice — date back to about 30,000 years ago.

"There is a huge difference between making three lines that any 3-year-old kid would be able to make and sculpting a Venus," Hublin, who was not involved in the study, told Live Science.Hublin said this discovery doesn't close the question of Neanderthals' cognitive skills. Proof that Neanderthals were capable of making a deliberate rock carving isn't evidence that they were regularly making art, he said.

"My own feeling is that if Neanderthals regularly used symbols, and given their longtime occupation throughout large parts of the Old World, we probably would have found clearer evidence by now," said Harold Dibble, an archaeologist at the University of Pennsylvania, who also was not involved in the study.

Dibble said he was convinced these markings were deliberate, but scientists need "more than a few scratches — deliberate or not — to identify symbolic behavior on the part of Neanderthals."

"Symbols, by definition, have meanings that are shared by a group of people, and because of that, they are often repeated," Dibble wrote in an email. "By itself, this is a unique example and without any intrinsic meaning … the question is not 'Could it be symbolic?' but rather 'Was it symbolic?' And to demonstrate that, it would be very important to have repeated examples." View Article Here Read More

While millions of people spent last weekend dumping buckets of ice water on their heads and documenting it on Facebook to raise money and awareness for ALS, a few us genetics geeks gathered and talked about haplogroups* A, L and S, among others.

*Never heard of a haplogroup? Don’t worry, it’s not because you have a brain freeze. A haplogroup is a branch on the human family tree. All people belong to a haplogroup based on genetic markers carried in their cells. People belonging to the same haplogroup trace their descent to a common ancestor and a specific place where that ancestor once may have lived.

Last Saturday morning at the first International Conference for Genetic Genealogy in Chevy Chase, Maryland, Genographic Project Director and National Geographic Explorer-in-Residence Dr. Spencer Wells delivered the Keynote to an audience of 300 genetic genealogists. He spoke about the popularity of the field and how fast consumer genetics has grown since the launch of The Genographic Project in 2005. “In 2013 the one-millionth person tested their DNA,” explained Wells, “just twelve years since the first human genome was sequenced. But this summer the two-millionth person has already tested their DNA.” The growth has been exponential, thanks in great part to the interest and promotion by those who gathered at the conference.

In addition to Dr. Wells, the Genographic Project was represented by Russian scientist, Dr. Oleg Balanovsky. Dr. Balanovksy talked about his efforts in mapping the world’s genetic diversity, and how his scientific partnership with the Genographic Project has informed questions like “If we are all related, where did our shared grandpas come from?”

Several leaders in the field of genetic genealogy also spoke, including Jim Bartlett, Katherine Borges, Rebekah Canada, Tim Janzen and Cece Moore. Doing his part to promote population genetics was blogger and PhD candidate Razib Kahn, who spoke about piecing together the puzzle that is ancient ancestry. Ancestry DNA was well represented by biologist Dr. Julie Granka who explained how they use DNA to help match their participants with relatives. And Dr. Joanna Mountain shared with the audience her efforts with 23andMe.

Razib Kahn talks about how we study ancestry through DNA. Photo by Miguel VilarOf the many topics discussed, it was clear that citizen science was the hot topic in this field. The public is generally more comfortable talking about their personal genomic details and a general interest in science has increased. As a result, people are encouraging friends and family to test and study their DNA. Who knows? As more people participate and find new connections and matches, genetic genealogy could become the new Facebook of science!View Article Here Read More

Assuming that we start counting from about 50,000 B.C., the time when modern Homo sapiens appeared on the earth (and not from 700,000 B.C. when the ancestors of Homo sapiens appeared, or several million years ago when hominids were present), taking into account that all population data are a rough estimate, and assuming a constant growth rate applied to each period up to modern times, it has been estimated that a total of approximately 106 billion people have been born since the dawn of the human race, making the population currently alive roughly 6% of all people who have ever lived on planet Earth. Others have estimated the number of human beings who have ever lived to be anywhere from 45 billion to 125 billion, with most estimates falling into the range of 90 to 110 billion humans.

Year

Population

50,000 B.C.

2

8000 B.C.

5,000,000

1 A.D.

300,000,000

1200

450,000,000

1650

500,000,000

1750

795,000,000

1850

1,265,000,000

1900

1,656,000,000

1950

2,516,000,000

1995

5,760,000,000

2002

6,215,000,000

Number who have ever been born

106,456,367,669

World population in mid-2002

6,215,000,000

Percent of those ever born who are living in 2002

5.8

The above estimate shows that about 5.8 percent of all people ever born are alive today. That’s actually a fairly large percentage when you think about it. Source: Population Reference Bureau estimates.

Number of people who have ever lived

Estimates of “the total number of people who have ever lived” published in the first decade of the 21st century range approximately from 100 to 115 billion.

An estimate of the total number of people who have ever lived was prepared by Carl Haub of the Population Reference Bureau in 1995 and subsequently updated in 2002; the updated figure was approximately 106 billion. Haub characterized this figure as an estimate that required “selecting population sizes for different points from antiquity to the present and applying assumed birth rates to each period”. Given an estimated global population of 6.2 billion in 2002, it could be inferred that about 6% of all people who had ever existed were alive in 2002.In the 1970s it was a popular belief that 75% of all the people who had ever lived were alive in the 1970s, which would have put the total number of people who ever lived as of the 1970s as less than the number of people alive today. This view was eventually debunked.

The number is difficult to estimate for the following reasons:* The set of specific characteristics that define a human is a matter of definition, and it is open to debate which members of early Homo sapiens and earlier or related species of Homo to include. See in this regard also Sorites paradox. Even if the scientific community reached wide consensus regarding which characteristics distinguished human beings, it would be nearly impossible to pinpoint the time of their first appearance to even the nearest millennium because the fossil record is simply too sparse. However, the limited size of population in early times compared to its recent size makes this source of uncertainty of limited importance. * Robust statistical data only exist for the last two or three centuries. Until the late 18th century, few governments had ever performed an accurate census. In many early attempts, such as Ancient Egypt and in the Persian Empire the focus was on counting merely a subset of the people for purposes of taxation or military service.[108] All claims of population sizes preceding the 18th century are estimates, and thus the margin of error for the total number of humans who have ever lived should be in the billions, or even tens of billions of people. * A critical item for the estimation is life expectancy. Using a figure of twenty years and the population estimates above, one can compute about fifty-eight billion. Using a figure of forty yields half of that. Life expectancy varies greatly when taking into account children who died within the first year of birth, a number very difficult to estimate for earlier times. Haub states that “life expectancy at birth probably averaged only about ten years for most of human history”[106] His estimates for infant mortality suggest that around 40% of those who have ever lived did not survive beyond one year. [ Source: http://en.wikipedia.org/wiki/World_population ]

OXFORD, ENGLAND—A new study of Paleolithic stone tools from 17 sites in North Africa shows that between 130,000 and 75,000 years ago, there were at least four separate populations in the region, each with its own distinctive cultural traits, reports phys.org. Researchers led by University of Oxford visiting scholar Eleanor Scerii made 300,000 measurements on stone tools and combined the data with enviromental reconstuctions of prehistoric North Africa to analyze how modern human populations dispersed across the Sahara using ancient rivers and streams that no longer exist. "This is the first time that scientists have identified that early modern humans at the cusp of dispersal out of Africa were grouped in separate, isolated and local populations," says Scerii. "Our picture of modern human demography around 100,000 years ago is that there were a number of populations, varying in size and degree of genetic contact, distributed over a wide geographical area." According to Scerii, the team's work supports the theory that modern humans left Africa before 60,000-50,000 years ago.View Article Here Read More